Centrifugal phase contactor



3mm. V 195% Filed. Nov. 19, 1951 K. H. ZMBRHSKHE, JR

- CENTRIFUGAL PHASE CONTAGTOR 5 Sheets-Sheet l Jan. 7, 1958 K. H.ZABRISKEE, JR 2,819,014

\CENTRIFUGAL PHASE CONTACTOR Filed Nov. 19, 1951 3 Sheets-Sheet 2 Jun.7, 1958 K. H. ZABRI$KEE, JR

CENTRIF'UGAL PHASE CONTACTOR 5 Sheets-Sheet 3;

Filed NOV. 19 1951 United States CENTRIFUGAL PHASE CONTACTOR Kenneth H.Zabriskie, Jr., Wilmington, Del., assignor to ThezSharples Corporation,a corporation of Delaware This invention relates generally to a methodand apparatus for the countercurrent contact of liquids, andparticularly to the utilization of centrifugal force for contact andseparation purposes;

Many types of equipment are now used for liquid/liquid extraction. Onetype comprises a series of mechanicalmixers followed by gravity orcentrifugal separation, each operation of mixing and settlingconstituting one stage, with multiple stages created by a multiplicityofm'ixing and separating steps, fresh solvent being introduced into theseries in the stage most remote from the introduction of the feed ofliquid to be extracted. Mixing may be done with some form of mechanicalagitator or with pump recirculation. This system is faulty in that suchmixing gives relatively poor contact efficiency. Attempts to improvecontact by intensifying and prolonging the agitation frequently produceemulsions that are difficultor impossible to break.

Perhaps 'themostwidellyused device consists of a tower packed withselected material such as glass balls, Raschig rings, short cylinders,or other special ceramic shapes. The lighter liquid is introduced at thebottom of the tow'erand passes upwardly while the heavier liquid is fedat the top and passes countercurrently downward. Packing is ordinarilyselected of a kindthat one of the liquids will wet and thus comprise thedispersed phase, whereas the other comprises the continuous phase.

Other forms of extractors are well known in the art, but many of theserequire a great deal of fioor space and/or head room, and most of themare so constructed that cleaning deposits is a major and time-consumingoperation.

The principal object of this invention is to provide an improvedcountercurrent extraction or contact method and apparatus in which thereis continuous countercurrent fluid flow through successive separatingand mixing stages.

A further object of this invention is to provide animprovedcountercurrent centrifugal extraction or contact imethodiandapparatus that has highly efii'cient contacting and separation features,and a high potential throughput per" unit area.-

A further object of the invention is to provide an improved centrifugalcountercurrent contactor having a plurality of successive separating andmixing stages; the separating" stages being relatively long withrespectto the mixingstages to reduce turbulence in the central area of theseparating stages.

A further object of this invention is to provide a cent 'rifugalmethodand apparatus into which two liquids may be fed and through which theyflow in continuous countercurrentmanner, with one or more stages inwhich the liquids are intimately mixed, following which they areseparated in each stage by centrifugal force.

Another object of the invention is to provide a more eti'icientcountercurrent extractor that can be easily disassembled and cleaned.

.Fields in which this method and apparatus are most atent ice usefulinclude antibiotic production, including extraction from broth;extraction and purification of vitamins, hormones, aminoacids, and otherpharmaceuticals; separation of close boiling-point hydrocarbons, as inthe extraction of toluene or butadiene from hydrocarbon mixtures such ashydro-former efiiuent; extraction of oxygenated compounds from syntheticgasoline, and isomer separation of suchcompounds as the nitro-toluenes;recovery of organic acids such as citric, lactic, and acetic acid fromaqueous solutions; purification of such organic materials as rosin,glycerine; washing of gasoline distillates to remove sulfur andmercaptans; vegetable oil fractionation; water cleanup of dilutesolutions of aniline, phenol, cresol.

In order that the invention may be more readily understood, reference ismade to the accompanying drawings, forming part of this specification,in which Fig. 1 is a vertical section of a centrifugal countercurrentcontactor illustrating one form of the invention;

Fig. 2 is an enlarged longitudinal sectional detail showing two mixingzones and an interposed separating zone of the device of Fig. 1;

Fig. 3 is a transverse sectional detail as seen at 3, 3 of Fig. 2;

Fig. 4 is a perspective showing the vane assembliesas used in thestructuresofFigs. 1-3;

Fig. 5 is a sectional detail similar to Fig. 2 in which the vanes arereplaced by'a' fibrous material.

Fig. 6 is a transverse sectional detail as seen at 6, 6 of Fig. 5;

Fig. 7 is a sectional detail similar to Figs. 2' and 5, but showing amodified vane construction";

Fig. 8 is a transverse sectional detail as seen at 8-3 of Fig. 7; t

Fig. 9 is a view corresponding to Figs. 5 and 7show ing a furthermodified construction for the separating stage in which a plurality ofdiscs are used;

Fig. 10 is a transverse sectional detail as seen at 1010 of Fig. 9; and

Fig. 11 is a perspective of one of the discs shown in Figs. 9 and 1'0.

The invention comprises essentially the provision in a countercurrentcentrifugal contact machine of a plurality of axially spaced separatingchambers "or stages in the rotor. These chambers have various rnedia forinducing or increasing separation therein and each separating chamber isadjacent to a mixing stage or chamber.

Referring now to the drawings, a centrifugal countercurrent contactmachine constructed in accordance with the present invention has a rotorassembly 10 which is turned at high speed by means of a driv'eshaft 11connected to the rotor top 12 by a shoulder nut 13. The rotor bottom 14is provided with an axial extension 15, which is journaled in a bearing16. Vertical support for bearing 16 is provided through a compressionspring 17 which acts between the bearing 16 and a collar 18 mounted inthe lowersupporting plate 19. A cup retainer 20 for the bearing is alsothreadedto the collar 18.

Both the heavy and light liquids are fed from the bottom of the machinein the present embodiment. However, it will be understood thatit isentirely possible to feed one or both of the liquids from the top ifdesired. The heavy liquid is introduced through a conduit 25 and fitting26 to the central feed pipe 27 for the rotor. However, feed pipe 27 isprovided with an axially extending bafile or wall 28 which forms asecondary feed pipe 29 for the heavy liquid. Secondary pipe 29 feedsliquid through orifice 30 into the chamber 31 which is provided withaccelerating vanes 32, 32 that rapidly propel the heavyliquid outwardlyand upwardly through a plurality of passages 33 into the rotor body 10.The heavy liquid then flowsupwardly and through successivesepaa ratingzones or stages 35, 36, 37 and 38 from which it flows around a flange 39on the rotor top 12 and upwardly through a plurality of passages 40, 40.It will be noted in Fig. 1 that passages 40 are tilted with respect tothe center line of the rotor so that the upper or discharge ends of thepassages 40, 40 are relatively closer to the center line than the lowerintake ends thereof.

The depth or thickness of the heavy liquid or phase in the rotor iscontrolled by the inside diameter of a ring dam 41 which is retained onthe rotor top 12 by a shoulder nut 42 and is provided with a gasket 43.The heavy liquid flows over ring dam 41 and nut 42 and into an annularcollecting chamber 44 supported on the upper plate structure 45. Chamber44 is provided with a suitable spout 46 from which the heavy liquid isultimately discharged.

The light liquid is also introduced into central feed pipe 27 throughconduit 50 and fitting 51 but in this case the light liquid flowsupwardly and out the top of the central feed pipe 27 into a chamber 52in the rotor top 12. The upper part of the feed pipe 27 is journaled inupper rotor bearing 53 which is retained in the rotor top 12 by means ofa flanged sleeve 54. The light liquid fiows into the rotor through aplurality of passages 55 which communicate with chamber 52 and therotor.

The total depth or thickness of the heavy and light liquid layers orphases is controlled by the inside diameter of a removable ring dam 56mounted in the rotor bottom 14. After flowing over ring dam 56 the lightliquid is discharged through passages 57 into the lower collectingchamber 58 from which it is removed through the lower spout 59. Thelower chamber 58 and its associated spout are supported on a platestructure 60 and the lower end of central feed pipe 27 together with itsassociated stationary structure may be supported by a member 61.

As previously stated, the inside diameter of ring dam 41 in rotor top 12controls the thickness of the heavy liquid in the rotor. The totalthickness of liquid, however, is controlled by the inside diameter ofring dam 56 in bottom 14 since the lighter liquid is radially nearer theaxis of rotation of the rotor. The location of the dividing line betweenthe heavy and light phases depends on the ratio of the total pressure ofthe light and heavy phases beneath flange 39 of rotor top 12 and thepressure of the heavy phase above flange 39 as determined by the insidediameter in ring dam 41. Increasing the inside diameter of dam 41displaces the dividing line between the light and heavy phases outwardlyin the rotor, thus reducing the thickness of the heavier layer.Decreasing the inside diameter of ring darn 41 increases the thicknessof the heavy layer and similar variations in the inside diameter of ringdarn 56 likewise control the thickness of the light liquid or phase andtherefore the total thickness of the liquid in the rotor. The smallerthe diameter the greater the total liquid thickness.

The light and heavy liquids or phases are, of course,

of different density, and are at most only partially miscible.

In general, the foregoing description is directed to the structure of acountercurrent centrifugal contactor and forms no part of the presentinvention. In a contactor of this type, however, it becomes veryimportant to obtain maximum efliciency and contact area between minuteparticles of the liquids. It has been found that satisfactory operationrequires several stages in which the liquids are successively separatedand mixed. The reason that several stages provide greater efiiciency perstage is not completely understood but it is believed that the transfercoefiicient is at a substantial maximum immediately after agitation andthat continued agitation beyond a specified time interval does notmaterially increase transfer. However, coalescence followed by furtheragitation permits additional transfer. For several reasons it isdesirable to incorporate the above-mentioned separating and mixingstages in a single centrifugal machine rather than utilizing separatemachines for each stage. Possible phase separating stages or zones35-38.

disadvantages incident to placing mixing and separating zones side byside in the same rotor are overcome or minimized in the presentconstruction with the result that additional transfer above theequilibrium value for a single stage can be achieved. The presentmachine provides marked increase in efliciency and reduction in costcompared to other known type of unitary countercurrent machine andcompared to separate machines for each stage. The two most importantfactors in achieving this increased efiiciency reside in thepredominantly unidirectional flow of each liquid phase throughout therotor and the ratio of the length of the separating zones with respectto the mixing zones.

In operation the heavy liquid is introduced to the bottom of rotor 10through passages 33, 33 from whence it flows radially outward to theperiphery of the first separating zone 35. This zone, together with theother separating zones, is provided with vane or wing assemblies 65 and65a which materially assist the separation. Thence the heavy liquidtravels upwardly through the successive mixing and separating stages orzones 66, 36, 67, 37 and 68 into the last separating zone 38.

The flow path of the light liquid from passages 55 in the rotor top isthe reverse of that just described for the heavy liquid.

It will thus be understood that there is in the present machine an outerannular layer of heavy liquid continuously moving upwardly in the rotorthrough the separating stages and an inner layer of light liquid movingin the opposite direction through the separating stages. The directionof movement of each of these layers is not altered nor changed but inthe mixing stages or zones flow in the rotor so that there is noappreciable variation in the direction thereof, nor is there appreciablevariation in the angular velocity of one liquid with respect to theother, for whatever change occurs in the angular velocity of one liquidin the mixing zones is shared by the other, and since the two liquidsrotate at at least substantially the same angular velocity in theseparating zones, the countercurrent flow of the phases with respect toeach other is under substantially the same relative angular velocityconditions.

Each of the mixing stages or phase mixing means 66, 67 and 68 comprisesa stationary member or blade 70 which is mounted transversely of therotor on the periphery of the central feed pipe or member 27 andretained thereon by a plurality of removable collars 71, 72, 72. Theblades 70 and collars 71, 72 are held in place by a nut 73 which isthreaded onto the feed tube 27 and compresses the blades and collarsagainst an abutment 74 in the bottom separating stage 35. The vaneassemblies 65 and 65a are held in place by the rotor top 12 and areaxially spaced at the mixing zones 66, 67 and 68 by spacers 76, 76 whichdefine the length of the mixing zones.

It will be understood that turbulence in and contiguous to the variousphase mixing stages or zones 66-68 will be carried over to a more orless limited extent into the It is therefore important that the axiallength of the separating stages be sufiicient to provide relativelystable separating conditions in a central area of the separating stages.It will be noted that the terminal separating stages 35 and 38 areshorter than the central stages 36 and 37. Since there is a turbulentmixing zone at only one end of the terminal separating stages it is notnecessary that they be so long as the central separating stages whichhave turbulence carried over into them from each end. Therefore thelength of the terminal separating zones need only be approximatelyone-half the length of the central separating zones. If no vaneassemblies 65, 65a or any equivalent devices are used in the separatingstages the length of the stages would be excessive. Therefore it hasbeen found that turbulence and increased separating efiicrency can beprovided in a rotor of reasonable length if the separating zones orstages as defined generally by the axial length of the vaneassembliesare at least three times the axial length of the mixing zonesor stages.

From the foregoing it can be seen that the respective phases enter themixing zones from opposite directions under conditions of countercurrentflow; that one phase is intimately dispersed in the other in said mixingzones; that said phases leavesaid mixing zones in admixture due to theturbulence created; and that the admixture is separated on each side ofa mixing zone to maintain predominantly countercurrent flow.

Referring to Fig. 4 it will be noted that the preferred main assembliescomprise a central sleeve 65!) to which three radially extending vanesor wings 65c, 650 are secured as by welding. When three vanes are usedthey are preferably spaced at 120 angles to each other. The onlydifference between assembly 65 and 65a is that the longer assemblies 65,65 are used in the longer central stages 36 and 37.

Figs. 5-11 illustrate other expedients which may be used in place of thevane assembly 65 in the separating stages for the purpose of increasingseparation and/or reducing turbulence therein. Fig. 5 shows the use of aseparating stage assembly that comprises a central sleeve 80 which isformed integrally with or welded to a perforated disc 81 at each end.The discs and the sleeve in effect form a spool and when used in placeof the vane assemblies of Fig. 4 are compressed in the rotor by top 12and spaced from each other by collars 76, 76. The separating zonedefined by the annular space between the discs 81, 81 is filled with afibrous material 83 such as glass Wool.

Figs. 7 and 8 illustrate a further modified construction for theseparating stages in which a plurality of spiral vanes 85, 85 aresecured to a central sleeve 86. The vanes are radially spaced withrespect to each other by means of a series of spacers 87, 87 as shown inFig. 8.

Figs. 9-11 illustrate a still further type of separating stage that maybe found useful in which a plurality of conical perforated discs 90 arestacked in the zone. Spacing between the discs is achieved by a seriesof annular spacing rings 91, 91 around the outer periphery of the discs.In this form the mixing blades 70a, 70a are bent to provide suitableclearance between discs in adjoining separating stages. It will be notedthat ample circulation for the outer layer of heavy liquid is providedthrough the outer ring of perforations 92, 92 and fiow of the innerlayer of light liquid is through the inner ring of perforations 93, 93.

It will be noted in all of the figures of the drawings that the variousmixing blades extend through what would be the normal interface betweenthe ligher and heavier phases if the various mixing zones were notprovided. This is more clearly illustrated in Figures 9 and 10, and canbe readily seen from the description of Figure 1.

It will thus be understood that I have provided an improved apparatusand process which permits substantial increase in efficiency in thecountercurrent separating and contacting of liquids. The presentconstruction permits quick disassembly of the rotor for proper cleaningwhich becomes highly important when the liquids tend to decompose or toleave deposits. Frequent cleaning to avoid contamination of the productis essential in certain instances.

While embodiments of the process and apparatus have been moreparticularly described, it is to be understood that this is by way ofillustration, and that changes, omissions, additions, substitutionsand/or modifications may be made by persons skilled in the art uponbecoming familiar herewith, and without departing from the spirit of theinvention. For instance, for purposes of illustration, the heavier phaseis described as flowing upwardly through the rotor, while the ligherphase phase flows downwardly, and apparatusto effect this purpose'hasbeen particularly described. However, it will be well understood bypersons skilled in the art thatthe apparatus may be modified in a mannerto cause the heavier phase to flow downwardly while the lighter phaseflows upwardly through the rotor. Then too, the rotor may revolve aboutan axis otherwise positioned such as horizontal, which also will be wellunderstood. Also for purposes of illustration, with accompanyingsimplicity of construction, the feed pipe 27 has been described as beingheld stationary along with the mixing blades 70 mounted thereon. Since,broadly speaking, all that is required is relative rotational movementbetween the rotor and the blades 70, it follows that such relativerotational movement may be brought about in any desired Way. Thus blades70 may be caused to rotate either in the same direction as the rotor butat a different rate, or in a direction opposite to the direction ofrotation of the rotor. These variables in relative rotational movementbetween the mixing devices or blades and the rotor make available anydesired degree of mixing or agitation, irrespective of the speed ofrotation of the rotor, with increased versatility in the application ofthe invention. Many other modifications or embodiments will suggestthemselves to persons skilled in the art upon becoming familiarherewith.

I claim:

1. A countercurrent centrifugal contactor comprising a rotor, means forfeeding a liquid phase to one end of said rotor, means for feedinganother liquid phase to the other end of said rotor, means at each endof said rotor for centrifugally separating said phases, means fordischarging said phases in separated condition from said rotor, meansfor maintaining predominantly unidirectional flow of each phase throughsaid rotor and countercurrent flow of said phases with respect to eachother under substantially the same relative angular velocity conditions,and means intermediate the ends of said rotor for intimately mixing saidphases while undergoing said countercurrent flow.

2. In a counter-current centrifugal contactor having a rotor, means fordriving said rotor, and means for flowing partially miscible liquidphases of different density countercurrently through said rotor, theimprovement which comprises means for flowing each of said phasespredominantly unidirectionally through said rotor in contact with theother of said phases, means in said rotor at each end thereof forcentrifugally separating said phases, means intermediate saidlast-mentioned means for intimately mixing said phases, said mixingmeans comprising a mixing member positioned transversely of said rotor,and means for effecting relative rotational movement between said mixingmember and said rotor.

3. In a countercurrent centrifugal contactor having a rotor, means fordriving said rotor, and means for flowing partially miscible liquidphases of different density countercurrently through said rotor, theimprovement which comprises means for flowing each of said phasespredominantly unidirectionally through said rotor in contact with theother of said phases, means in said rotor at each end thereof forcentrifugally separating said phases, a plurality of spaced phase mixingmeans intermediate said last-mentioned means, each said phase mixingmeans comprising a mixing member positioned transversely of said rotor,means for effecting relative rotational movement between said mixingmember and said rotor, and a phase separating zone positioned in saidrotor between adjacent phase mixing means.

4. A countercurrent centrifugal contactor comprising a rotor, means forfeeding a liquid phase to one end of said rotor, means for feedinganother liquid phase to the other end of said rotor, means within saidrotor for maintaining predominantly unidirectional flow of each phasethrough said rotor and countercurrent flow of said phases with respectto each other under substantially the same relative angular velocityconditions, a plurality of axially spaced phase mixing zones within saidrotor for intimately mixing said phases while undergoing saidcountercurrent flow, a plurality of axially spaced phase separatingzones in said rotor, each phase mixing zone having a phase separatingzone on each side thereof, and means for discharging said phases inseparated condition from said rotor.

5. In a countercurrent centrifugal contactor having a rotor and meansfor driving said rotor, the improvement that comprises a heavy liquidinlet at one end of the rotor,

a heavy liquid outlet at the opposite end of the rotor, a light liquidinlet at the same end of the rotor as the heavy liquid outlet, a lightliquid outlet at the same end of the rotor as the heavy liquid inlet,means for effecting flow of each liquid from one end of the rotor to theother in a direction opposite to and in contact with the other liquid, acentral member extending into the rotor, a mixing member mounted on saidcentral member against which mixing member the heavy liquid is fed fromone side and the light liquid is fed from the other side, means foreifecting relative rotational movement between said rotor and saidcentral member, and means on each side of said mixing member forseparating said liquids and for maintaining predominantly unidirectionalflow of each liquid during their countercurrent flow.

6. The apparatus of claim wherein the means on each side of saidmixingmember for separating said liquids includes a vane assemblyrotatable with the rotor.

7. The apparatus of claim 5 wherein the means on each side of saidmixing member for separating said liquids includes a mass of fibrousmaterial mounted in the rotor to rotate therewith.

8. Apparatus in accordance with claim 7 in which the fibrous material isglass wool.

9. The apparatus of claim 5 wherein the means on each side of saidmixing member for separating said liquids includes a plurality ofconical discs mounted for rotation with said rotor.

10. The apparatus of claim 5 having a plurality of mixing members spacedaxially of the central member with each mixing member having aseparating zone on each side thereof for separating said liquids.

11. Apparatus in accordance with claim 10 in which the centralseparating zones are relatively longer than the terminal separatingzones.

12. Apparatus in accordance with claim 10 in which the separating zonesare provided with separating means which reduce turbulence in theseparating zones, said separating means terminating in spaced axialrelation on either side of the mixing members to define a mixing zone.

13. Apparatus in accordance with claim 12 in which the axial length ofthe separating zones is at least three times the axial length of themixing zones.

7 References Cited in the file of this patent UNITED STATES PATENTS2,072,382 Robinson Mar. 2, 1937 2,234,921 Webb Mar. 11, 1941 2,705,594Brewer Apr. 5, 1955 FOREIGN PATENTS 659,241 Great Britain Oct. 17, 1951

